Does your garage door keep reversing before it could even touch the floor? There must be something obstructing the safety sensor located at the bottom of your door. This small infrared sensor passes a beam a few inches off your floor from side to side and if an object interrupts or break it, your door will definitely reverse.
This is actually a simple fix. The lens is likely attached to the metal brackets connected to the door frame. Just remove whatever is obstructing the beam. It can be a leaf or a small piece of paper. Take time to clean the eye with a soft cloth as well.
This problem can also be a result of a close-force screw that is not properly adjusted. For less sensitivity and to avoid friction from the door rollers that could make your opener think that the door has reached the floor, you must ensure that it is adjusted perfectly.